54 
This statement is much overdrawn, but the fact remains that con- 
siderable damage may result if the ravages of this species should ex- 
tend to plantations and not be controlled. 
The Loranthacese are chlorophyllaceous plants. They obtain their 
supply of water, nitrogen, mineral salts, etc., from the host. This 
material is elaborated in the stems or leaves in the same manner as 
in other green plants. They are consequently semiparasitic. The de- 
gree of parasitism, however, varies with the species. In some the 
amount of chlorophyll is much less than in others. The reduction 
of chlorophyll, together with the absence of leaves, develops a para- 
sitic condition much greater than is the case in the green-stemmed 
leafy species. Dendrophthom poeppigii belongs to the former group 
and is comparable to the strongly parasitic species of Iiazoumofskya, 
so destructive to conifers in the western United States. In fact, both 
are capable of maintaining their existence in the wood and bast with- 
out aerial parts during the entire life of the hosts. This requires a 
completely submerged root system. In contrast to most tropical 
loranths, which send out roots from the gnarled point of attachment 
along the outside of the branch, giving off at short intervals stout 
suckerlike roots which penetrate the cortex, the Hevea mistletoe 
sends its roots directly into the cortex at the point of the germina- 
tion of the seed and does not later produce surface roots. This is 
characteristic of all species in the Temperate Zone and results in 
the formation of burls and cankers and causes the death of branches 
beyond the point of infection. 
The seeds of the mistletoes are provided with a mucilaginous coat- 
ing which causes them to adhere to any object upon which they may 
fall or may be placed. The primary root of the germinating seed 
develops a terminal disk or sucker which is pressed firmly on the sub- 
stratum. From the center of this sucker a root or sinker appears 
which penetrates the cortex. It is a very delicate structure and ter- 
minates its apical growth when it reaches the wood. This root, 
however, is provided with meristematic tissue in the region of the 
cambium of the host. By intermediary growth the root is able to 
elongate at the same rate as the increase of the branch in thickness. 
As the apex of the root is buried deeper each year by the increased 
increment of the host, the root appears to have actually forced its 
way into the wood (PL XXVII). These roots remain functional 
for a greater or lesser period of time, depending on the nature of the 
substratum. Frequently in the beginning they are joined with the 
medullary rays and function for a longer period. Sections through 
the wood of the host show these roots in various stages of groAvth 
and disintegration. In the region of the fast, lateral roots grow hori- 
zontally from the original root, and a network of cortical stroma is 
developed which stimulates the host tissues to form abnormal struc- 
tures. This eventually results in the formation of dead wood and 
open cankers, to the great detriment of the host. 
The general nature of the injury by mistletoes on Hevea is ex- 
pressed in a gradual reduction of the leaf surface of the host, which 
causes a reduction of growth in height and diameter. New infec- 
tions take place through the agency of a germinating seed, which 
reaches the point of infection usually through birds, which use the 
pulp of the berries for food, or by the extension of the submerged 
